Many of described the current struggle against terrorism as "a clash of civilizations". Al Qaeda and its ilk are not a civilization. They are nihilists with a romantic yearning for a non-existent past. It is more a struggle of good and evil: those who would build and those who would destroy. Unfortunately, some of the "good" think only in destructive terms.
Although Rupert Smith, a retired British general, doesn't discuss the Iraq war in The Utility of Force: The Art of War in the Modern World, he makes many points that are instructive for this conflict. Essentially, "Smith argues that the military aims of the West are fundamentally at odds with the structure of Western military organizations, a contradiction which leads military operations into difficulty and potential failure." See "On War and Politics", Robert Farley, American Prospect, July 13, 2007.
Or as Abraham Lincoln said, "As our cause is new, so must we think anew."